Injector Knock?
 

My truck has a knock sound, like valves. I took it to a highly recommended diesel shop and they listened to it and said it was normal and that it was the injectors loading up on the next power band. It happends right about 1600rpm and then smooths out and nearly goes away with higher rpm's. It sounds really quiet and smooth 1600 and below. Does this sound right?

Did they run any tests? Sounds like you need to avoid this shop in the future.

No, just listened on a drive test. Is there something that comes to mind as to what the problem may be?

:argh: Dont go back there...

Hard to say... Need to do a buzz test, cylinder contrbution test, Rotational value test... Check the fuel pressure...

A test drive will tell you squat.

Thats all I asked them to do, just wanted to know if it sounded right, the performance feels good so the only other reason I would want it checked out was if it didnt sound right. They said it sounded fine so there was no reason to check anything out, sounds good feels good, but in the back of my mind I just kept thinking it didnt sound right, but I dont know much about diesels. I have noticed that when you are cruising around 40-45mph and you let off the throttle that when the tc lets go the tach falls back to an idle but you dont hear the engine for a couple of seconds, then it sounds like it is loping for a few seconds then perfect idle. It has no excessive amount of blowby(checked the crude way, upside down oil fill cap) runs smooth, has good power, good oil pressure, good egt's, good boost, still checking on the fuel mileage. Are there threads on here that explain how to do those tests and what you need to do them or are those things only high dollar equipment and years of book learnin can do?

In my sig there is a link to a site for Auto Enginuity... Its a great tool that can run all the tests a Ford shop can right off your laptop.

Most of what your explaining does sound normal, when coasting the injectors will actually turn off and not fire at all from time to time.

My 2000 does it as well. Cruising around with the windows down, it sounds like I have .100" valve lash under certain loads/RPM. It IS injector cackle and the sole reason for the "long-lead" injector that Ford started installing in the 99-00 trucks under warranty in '01 (and installed from the factory in early '01 and later build trucks).

If this is what they told you..... :argh:

Speaking of valve lash, what should it be, (I dont know how bad .100" is)? What is a long lead injector? What is the difference between the injectors? What is going on with mine if it is cackle, how bad is it, what do I do to fix it or is it just something I live with?

The valve lash is not adjustable in these engines. The rocker pedestals bolt securely to the head and they have hydraulic lifters.

The "long lead" injector is internally different from the other 7 injectors in the engine as it allows for the reduction in available high pressure oil and fuel in the number 8 cylinder after number 6 fires. Number 6 is actuated right before number 8 in the firing order and they happen to be right next to each other in the engine. Basically, number 6 steals fuel and oil pressure from #8.

Nothing wrong with cackle...it's just annoying. Ford's idea of "dead-heading" the fuel in the cylinder head in the 99-03 trucks wasn't the best thing to do. It won't hurt anything.

Turn up the radio!

The rattle doesnt bother me unless there is something wrong. Why does it come in so sharply at 1600rpm's? Kinda funny to watch all the mexicans jump when my truck rolls up because it sounds like the foremans truck on most ranches, :lol: